Crude extracts of rat atria containing potent diuretic and natriuretic substances have been previously referred to as atrial natriuretic factor [A. J. deBold et al, Life Sci., 28, 89-94 (1981)]. These substances have subsequently been chemically defined as peptides, commonly referred to as atrial natriuretic peptides or ANP.
Various peptides of related structures have been isolated, sequenced and shown to have natriuretic, diuretic and vasorelaxant activity in varying degrees. A group of atrial peptides of significant interest, known as Atriopeptins I, II and III (AP-I, AP-II and AP-III), are described, for example, in publication of Geller et al, Biochem. Biophys. Res. Commun., 120 (2), 333-338 (1984), and in U.S. Pat. No. 4,496,554 to Needleman. These peptides are in the oxidized, that is, cyclized form, and have the following amino acid sequences: